This invention relates to a process for the catalytic reaction of olefin(s) with alcohol(s) to provide ether(s). More particularly, the invention relates to a process for the reaction of one or more light olefins such as ethylene, propylene, butene(s), pentene(s), hexene(s), heptene(s), etc., or mixtures thereof, with one or more lower alkanols, e.g., methanol, ethanol, n-propanol, isopropanol, etc., or mixtures thereof, to provide one or more ethers employing the acidic form of a particular synthetic porous crystalline materials, or zeolite, as catalyst. The product ether(s) are useful, inter alia, as high octane blending stocks for gasoline.
Zeolitic materials, both natural and synthetic, have been demonstrated in the past to have catalytic properties for various types of hydrocarbon conversion. Certain zeolitic materials are ordered, porous crystalline aluminosilicates having a definite crysatlline structure as determined by X-ray diffraction, within which there are a large number of smaller cavities which may be interconnected by a number of still smaller channels or pores. These cavities and pores are uniform in size within a specific zeolitic material. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions, these materials have come to be known as "molecular sieves" and are utilized in a varity of ways to take advantage of these properties. Such molecular sieves, both natural and synthetic, include a wide variety of positive ion-containing crystalline silicates. These silicates can be described as a ridid three-dimensional framework of SiO.sub.4 and Periodic Table Group IIIA element oxide, e.g., AlO.sub.4, in which the tetrahedra are cross-linked by yhr sharing of oxygen atoms whereby the ratio of the total Group IIIA element, e.g., aluminum, and silicon atoms to oxygen atoms is 1:2. The electrovalence of the tetrahedra containing the Group IIIA element, e.g., aluminum, is balanced by the inclusion in the crystal of a cation, e.g., an alkali metal or an alkaline earth metal cation. This can be expressed wherein the ratio of the Group IIA element, e.g., aluminum, to the number of various cations, such as Ca/2, Sr/2, Na, K or Li, is equal to unity. One type of cation may be exchanged either entirely or partially with another type of cation utilizing ion exchange techniques in a conventional manner. By means of such cation exchange, it has been possible to vary the properties of a given silicate by suitable selection of the cation. The spaces between the tetrahedra are occupied by molecules of water prior to dehydration.
Prior art techniques have resulted in the formation of a great variety of synthetic zeolites. Many of these zeolites have come to be designated by letter or other convenient symbols, as illustrated by zeolite Z (U.S. Pat. No. 2,882,243); zeolite X (U.S. Pat. No. 2,882,244); zeolite Y (U.S. Pat. No. 3,130,007); zeolite ZK-5 (U.S. Pat. No. 3,247,195); zeolite ZK-4 (U.S. Pat. No. 3,314,752); zeolite ZSM-5 (U.S. Pat. No. 3,702,886); zeolite ZSM-11 (U.S. Pat. No. 3,709,979); zeolite ZSM-12 (U.S. Pat. No. 3,832,449); zeolite ZSM-20 (U.S. Pat. No. 3,972,983); zeolite ZSM-35 (U.S. Pat. No. 4,016,245); and zeolite ZSM-23 (U.S. Pat. No. 4,076,842), merely to name a few.
The SiO.sub.2 /Al.sub.2 O.sub.3 ratio of a given zeolite is often variable. For example, zeolite X can be synthesized with SiO.sub.2 /Al.sub.2 O.sub.3 ratios of from 2 to 3; zeolite Y, from 3 to about 6. In some zeolites, the upper limit of the SiO.sub.2 /Al.sub.2 O.sub.3 ratio is unbounded. ZSM-5 is one such example wherein the SiO.sub.2 /Al.sub.2 O.sub.3 ratio is at least 5 and up to the limits of present analytical measurement techniques. U.S. Pat. No. 3,941,871 (Re. 29,948) discloses a porous crysalline silicate made from a reaction mixture containing no deliberately added alumina in the recipe and exhibiting the X-ray diffraction pattern characteristic of ZSM-5. U.S. Pat. Nos. 4,061,724, 4,073,865 and 4,104,294 describe crystalline silicates of varying alumina and metal cotent.
There is a need for an efficient catalytic process to manufacture ethers from the reaction of light olefins with lower alkanols augmenting the supply of high octane blending stocks for gasoline. Relatively low molecular weight eithers such as methyl-t-butyl ether (MTBE) and t-amyl methyl ether (TAME) are in the gasoline boiling range and are known to have a high blending octane number. The petrochemicals industry produces mixtures of light olefin streams in the C.sub.2 to C.sub.7 molecular weight range and the coversion of such streams or fractions thereof to ethers can also provide products useful as solvents and as blending stocks for gasoline.
The reaction of light olefins with lower alkanols to provide ethers is a known type of process.
According to U.S. Pat. No. 4,042,633, diisopropylether (DIPE) is prepared from isopropyl alcohol (IPA) employing montmorillonite clay catalysts, optionally in the presence of added propylene.
U.S. Pat. No. 4,175,210 discloses the use of silicatungstic acid as catalyst for the reaction of olefin(s) with alcohol(s) to provide ether(s).
As disclosed in U.S. Pat. No. 4,182,914, DIPE is produced from IPA and propylene in a series of operations employing a strongly acidic cation exchange resin as catalyst.
In the process for producing a gasoline blending stock described in U.S. Pat. No. 4,334,890, a mixed C.sub.4 steam containing isobutylene is reacted with aqueous ethanol to form a mixture of ethyl tertiary butyl ether and tertiary butanol.
U.S. Pat. No. 4,418,219 describes the preparation of MTBE by reacting isobutylene and methanol in the presence of boron phosphate, blue tungsten oxide or crystalline aluminosilicate zeolite having a silica to alumina mole ratio of at least 12:1 and a constraint index of from 1 to about 12 as catalyst.
U.S. Pat. No. 4,605,787 discloses the preparation of alkyl tert-alkyl ethers such as MTBE and TAME by the reaction of a primary alcohol with an olefin having a double bond on a tertiary carbon atom employing as catalyst an acidic zeolite having a constraint index of from about 1 to 12, e.g., zeolite ZSM-5, -11, -12, -23, dealuminized zeolite Y and rare earth-exchanged zeolite Y.
European Patent Application 55,045 describes a process for reacting an olefin and an alcohol to provide an ether, e.g., isobutene and methanol to provide MTBE, in the presence of an acidic zeolite such as zeolite Beta, zeolites ZSM-5, -8, -11, -12, -23, -35, -43 and -48, and others, as catalyst.
German Patent No. 133,661 describes the reaction of isobutene and methanol to provide a mixture of products including MTBE, butanol and isobutene dimer in the presence of acidic zeolite Y as catalyst.
According to Japanese Patent No. 59-25345, a primary alcohol is reacted with a tertiary olefin in the presence of a zeolite having a silica to alumina mole ratio of at least 10 and the x-ray diffraction disclosed therein to provide a tertiary ether.